Electrical apparatus



IOfi. COMPOSITIONS,

COATING OR PLAST C I Drawing.

Patented Jan. 26, 1932 Cab es RIEFIEIiEN'CE UNITED STATES PATENT OFFICE mos a. novmr, or scorn, nirw roan, nssrenon r0 Gm nmermc comm,

a coaromrron or nnw roan The present invention relates to electrical apparatus and is concerned with the insula- 111011 of electrical conductors in such apparatus. More specifically it is concerned with the provision in a novel manner of inor anic insulation on electrical conductors.

' t is well known that inorganic insulation .onelectrical conductors, for example the coils of motors and generators, transformers and the like, is highly desirable for the reason that such insulation is more heat resistant, less liable to attack b chemical agents, and permits of the pro uction ot a more compact unit than does" organic insulation.

It 'has been recognized that one of the ma'or obstacles inthe way of the utilization of inorganic insulation has been the lack of flexibility of such insulation. Consequentl there has been great difliculty in applying t e insulation to conductors in such a manner \that it would not flake or chip ofl during winding of a coil, for example.

In accordance with my invention it is proi posed to provide electrical conductors with inorganic insulation before the conductors are wound into coils or otherwise formed into shapes necessary for the particular apparatus in which the are emplo ed. After the conductors are t us provide with the insulation, a coating or film of temporary protective material is applied which is characterized by the fact that it can be easily and completely removed from the conductors without injury to the insulation. The conductors are now wound into coils or formed into any desired shape. The protective coat is then removed leaving the conductors insulated with a film of inorganic insulation and spaced to receive insulation previously applied but imparts additional heat resistance thereto.

fMy invention will be better understood by any suitable well-known manner.

'mcrnrcn. Arrma'rus Application me m as, man Serial 10.853317.

tion thereof, its scope being pointed out in the appended claims.

The invention will be anal-ma by describing the process employed in connection with the manufacture of an electrical coil as representative of a shaped electrical conductor.

An electrical conductor, for exam 1e a wire of copper, is providedwith a coat 0 oxidein The insulated wire is now provided with a thin coat of alkyd resin. This may be accomplished by running the insulated wire through an enameling machine or by extruding a film of alkyd resin on the wire. Alkyd resins, as

is we known, comprise those complexes resulting primarily from the mterreactlonof a polyhydric alcohol, such as glycerine, and

a polybasic acid, such as phthalic acid or its anhydride, with or without other reacting in redients. The film of resin protectstheoxide fihn on the copper conductor against chip ing or flaking and from bein scraped off uring the winding process which next takes place. A coil may thus be wound without injuring the oxide insulation film which is practically impossible to avoid during winding of a coil with conductors covered with oxide insulation alone. Alkyd resins ma be obtained with varying degrees of flexibi ity; hence the alkyd resin protecting film is flexible in nature and will itself not crack" or flake off during the coil winding process. It thus adequately rotects the oxide film.

A characteristic 0 alkyd resins is that they volatilize with substantially no residue at a suitable elevated temperature. For example, at about 380-400 C. the resin may be completely volatilized. Hence by simply baking the coil at this temperature for a suitable period of time, for example, about two hours,

the resin film protecting the inorganic insulation is easily and completely removed. This leaves the inorganic insulating film intact and uninjured, and the wound coil is in position with spacing ready to receive further rigid and permanent insulation; Examples of solid inorganic insulation which may now be applie are the following: Mixtures of wa 1- 9 reference to the following detailed descripglass, asbestgs and flint: p laster of aris;

EXAMINER borate and mica, cast molten ures ead la or vi ls, and the like. 5 s an alternative material for the temporary spacing and protective coating a plastic material such as rubber, particularly unvulcanized rubber, possesses the desired proper ms or use in the process of the invention. The rubber may be ap lied to the insulated conductor in an suita le manner, for example by extrusion, d ip ing, etc. The dipping method a ears to e preferable inasmuch as less ruliher is deposited on the insulated wire and hence there is less rubber to remove after the coil is wound. Instead of heating to volatilize the temporary protective coatingas when an alk d resin is used, the rubber may be removed b y dissolving it in hot aliphatic hydrocarbon solvents therefor, for example, by heating at about 220 C. in hot transil oil. The traces of oil remaining on the conductors may be removed by washing in solvents after which the coil is ready to receive its final rigid insulation as described above.

Alk d resins and rubber are not only materials w ich may be employed as the temporary protective coat in the rocess of the invention. Other plastic and or flexible materials which may be applied to the conductors to rotect themduring manipulation into their finalshape and which may be removed without. injuiiy to the insulation may be emer and removed b heating the coated wire at about 400 two hours. 1

The initial inor anic'insulation applied to the conductor nee not be an oxide. I It may be such amaterial as lead borate or other suitable inorganic insulation. Of course, the conductor need not be copper. Any suitable .45 metal may be employe For example, aluminum may be used and provided with an for approximately imatmg coat comprising a film of aluminum oxide. Furthermore, a different oxide than that of the metal employed. may be provided on the conductor; for example, a copperconductor may be provided with an insulating film of aluminum oxide in accordance with the process outlined in the Letters July 26,1927. What I claim as new and desire to secure by Letters Patent of the United States is:

1. A process which comprises the steps of on providing a'metallic conductor with a coat-' with ployed. r exam le, metast rene ol mer' may be used in p ace of all g3 res ns and rub said protective coat and applying another coating of inorganic insulation.

2. A process of providing an electrical coil inorganic insulation which comprises insulating the metallic conductors from which the coil is to be formed, with inorganic insulation, coating the insulated-conductors with an alkyd resin, forming the coil, removing said alkyd resin coat from the conductors,

and impregnating the coil with additional inorganicinsulation.

3. A process of providing an electrical coil with inorganic insulation which comprises insulating the metallic conductors from which the coil is to be formed, with inorganic insulation, coating the insulated conductor with an alkyd resin, forming the coil, heating the coil at about 380400 C. for about two hours and impregnating the coil with additional inorganic insulation.

4. A rocess of providing an electrical coil wit inorganic insulation which comprises providing a film of oxide on a metallic conductor, providing said conductor with a film of lastic material which is removable from sai conductor without injury to the oxide filmthereon, winding said conductor into a coil, removin the plastic coat, and providing said coil w1th a rlgid inorganic insulation on and between the turns thereof.

5. In a process of forming an inorganically insulated electrical winding, the steps of providing electrical conductors, prior to the for- .mation of the winding with a coating of insuperposing on said. a temporary protective coat of a organic insulation an coatin matenal which is removable without injury to the inorganic insulation after the winding is formed.

' .6. In a process of forming an inorganically insulated electrical coil, the steps of providap lyin to said coated con uctors a film oi ru ber, ormin the coil, removing said rubber, and provi 'ng said coil with a rigid inorganic insulation on and between the turns thereof.

In witness whereof, I have hereunto set my hand.

ing of inorganic insulation, covering said inorganic insulation with a temporary protective coat of material which is removable without injury to said insulation, forming 06 the conductor "into a shape,

moi: e. HOVEY. 

